Game loaners and rentals.

General

I've yet to graduate from chairsofting to attending my first game. I am under-equipped for components; for example, my We Scar L CB has two mags, my We M&P Toucan has three, and I understand that'd never be enough to be effective in game. If I attend a game prior to purchasing more mags, is it common for popular mag types (like a We M4 CB) to be available to rent for the day?